The spectral characterization of polarization dependent loss (PDL) of locally pressed fiber Bragg grating is analyzed. Aimed at secondary peak phenomenon, the effects of the load magnitude, loaded length and loaded position of the grating on the amplitude and position of the created secondary peak are investigated in detail. The numerical simulation based on the modified transfer matrix method is carried on. The theoretical analysis and numerical simulation demonstrate that the loaded length has significant effect on the amplitude and sensitivity of wavelength shifting as function of loaded amplitude of the secondary peak. The load amplitude of creating secondary peak changes under the different loaded lengths. These studies have a good theoretical guidance meaning for sensing using secondary peak of PDL.